Posted by Alonzo on .
Rosea drives her car 30 kilometers to the train station, where she boards a train to complete her trip. The total trip is 120 kilometers. The average speed of the train is 20 kilometers per hour faster than that of the car. At what speed must she drive her car if the total time for the trip is less than 2.5 hours?

Precalculus 
FredR,
distance = velocity x time or
time = distance / velocity
total time=d1/v1+d2/v2=2.5 hrs (1)
where d1 = car distance = 30 (2)
v1 = car speed
d2 = train distance = 120  d1 (3)
v2 = train velocity = v1+20 (4)
combine (1), (2), (3), and (4) and solve for v1 
elementary 
Anonymous,
300 and 200000

Precalculus 
laura,
idk can you show me how please